Spinal implant

ABSTRACT

A spinal implant as provided having a porous body that includes a leading end, a convex trailing end and first and second sides extending between the leading and trailing ends. At least a portion of the leading end is generally straight. The body further includes a generally dome-shaped superior surface and a generally planar inferior surface. The superior surface is convex between the leading and trailing ends and is convex between the first and second sides.

CROSS REFERENCE

This application is a continuation of U.S. patent application Ser. No.11/770,087, filed on Jun. 28, 2007, which is a divisional of U.S. Designpatent application Ser. No. 29/277,225, filed Feb. 19, 2007, now U.S.Pat. No. D566,842, issued Apr. 15, 2008, the disclosures of which areexpressly incorporated by reference herein in its entirety.

FIELD OF THE INVENTION

The present invention relates generally to skeletal implants. Moreparticularly, the present invention relates to implants for stabilizingintervertebral joints.

BACKGROUND OF THE INVENTION

Chronic back problems cause pain and disability for a large segment ofthe population. In many cases, chronic back problems are caused byintervertebral disc disease. When an intervertebral disc is diseased,the vertebrae between which the disc is positioned may be inadequatelysupported, resulting in persistent pain. Stabilization and/orarthrodesis of the intervertebral joint can reduce the pain anddebilitating effects associated with disc disease.

Spinal stabilization systems and procedures have been developed tostabilize diseased intervertebral joints and, in some cases, to fuse thevertebrae that are adjacent the diseased joint space. Most fusiontechniques include removing some or all of the disc material from theaffected joint, and stabilizing the joint by inserting an implant (e.g.,a bone graft or other material to facilitate fusion of the vertebrae) inthe cleaned intervertebral space.

Spinal implants can be inserted into the intervertebral space through ananterior approach, a lateral (transverse) approach, a posteriorapproach, or postero-lateral approach. The anterior approach involves asurgeon seeking access to the spine through the front (i.e., abdominalarea) of the patient. The posterior approach involves a surgeon seekingaccess to the spine through the back of the patient. The postero-lateralapproach is similar to the posterior approach with access coming morefrom either or both sides of the patient. A variety of differentanterior, posterior and posterior-lateral techniques are known.

SUMMARY OF THE INVENTION

While the invention will be described in connection with certainembodiments, it will be understood that the invention is not limited tothese embodiments. On the contrary, the invention includes allalternatives, modifications and equivalents as may be included withinthe spirit and scope of the present invention.

A spinal implant is provided having a porous body that includes aleading end, a convex trailing end and first and second sides extendingbetween the leading and trailing ends. At least a portion of the leadingend is generally straight. The body also includes a generallydome-shaped superior surface and a generally planar inferior surface.The superior surface is convex between the leading and trailing ends andis convex between the first and second sides.

In other embodiments, the implant may include one or more of thefollowing features. The implant may further include a first openingextending through the implant from the superior surface to the inferiorsurface and a second opening communicating with the first opening andextending through the trailing end. The first and second openings areconfigured for receipt of an inserter instrument to insert the implantbetween vertebral bodies.

The inferior surface may have a generally trapezoidal shape. The firstand second sides may be generally straight and may diverge away from oneanother from the leading end to the trailing end. The body may be madeof metal. The leading end may be a posterior end and the trailing endmay be an anterior end.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated in and constitute apart of this specification, illustrate embodiments of the invention and,together with a general description of the invention given above, and adetailed description of the embodiments given below, serve to explainthe principles of the invention.

FIG. 1 is a front perspective view of a spinal implant according to oneembodiment of the present invention;

FIG. 2 is a top plan view of the implant shown in FIG. 1;

FIG. 3 is a cross-sectional view taken along line 3-3 in FIG. 2;

FIG. 4 is a front elevational view of the implant shown in FIGS. 1-3;

FIG. 5 is a side elevational view of the implant shown in FIGS. 1-4;

FIG. 6 is a bottom view of the implant shown in FIGS. 1-5;

FIG. 7 is a rear elevational view of the implant shown in FIGS. 1-6.

DETAILED DESCRIPTION

The present invention is directed to skeletal implants and methods forplacing implants between bones desired to be fused. It is preferred forthe implants to be used for vertebral/spinal applications such as fusingcervical, thoracic and/or lumbar intervertebral joints. In the case offusing an intervertebral joint, implants in accordance with theprinciples of the present invention can be implanted using an anterior,posterior or postero-lateral approach to the patient's vertebrae.

As used herein, an “implant” includes any implant suitable forfacilitating fusion between adjacent bones and includes implantsprepared from known implant materials including, non-bone material suchas titanium, stainless steel, porous tantalum or other metal, bio-glass,calcium phosphate, ceramic, carbon fiber-based polymers andbiodegradable polymers.

FIGS. 1-7 illustrate a spinal implant 10 according to one embodiment ofthe present invention. Implant 10 includes a body 12 having a leadingend 14, a convex trailing end 16 and first 18 and second 20 sides thatextend between the leading 14 and trailing 16 ends. Leading end 14 mayinclude rounded, or radiused portions, indicated at 21, that blend withsides 18, 20. Leading end 14 may be generally straight between therounded portions 21. The body 12 further includes a generallydome-shaped superior surface 22 and an inferior surface 24 that may begenerally flat. The superior surface is convex between the leading 14and trailing 16 ends and is also convex between sides 18, 20.Accordingly, the superior surface is convex in both ananterior-to-posterior direction and a medial-to-lateral direction.

Implant 10 further includes an opening 26 that extends completelythrough implant 10 from the superior surface 22 to the inferior surface24. Implant 10 also includes an opening 28 that communicates withopening 26 and extends through the trailing end 16. The function ofopenings 26, 28 are described below. In an exemplary embodiment,openings 26 and 28 may be generally oval-shaped. However, one or both ofopenings 26, 28 may have other shapes within the scope of the presentinvention.

As shown in FIG. 4, implant 10 has a height “H.sub.1” extending betweenthe highest point on the superior surface 22 and the inferior surface24. Implant 10 also includes length “L” that extends between the leadingend 14 and the location on trailing end 16 that is the farthest awayfrom leading end 14. A first width “W.sub.1” exists between sides 18, 20at the trailing end 16 and a second width “W.sub.2” exists between sides18, 20 at the leading end 14. Sides 18 and 20 may diverge away from oneanother between the leading 14 and trailing 16 ends, as shown in FIGS. 2and 6. Accordingly, the inferior surface 24 has a generally trapezoidalshape and width “W.sub.1” is greater than width “W.sub.2”. Themagnitudes height “H”, length “L” and widths “W.sub.1” and “W.sub.2” mayvary with application.

In an exemplary embodiment, implant 10 may be inserted into a cervicaldisc space to fuse adjacent cervical vertebrae. Also, in an exemplaryembodiment, implant 10 may be inserted using an anterior approach, suchthat leading end 14 is a posterior end and trailing end 16 is ananterior end. In this event, a distal end, or key of an instrument, suchas an inserter (not shown) may be inserted into opening 28 such that awidth of the key initially extends generally along a longitudinal axis30 of opening 28. When the inserter is inserted farther into implant 10,the key of the inserter reaches the intersection of openings 26 and 28.The inserter may then be rotated 90 degrees such that the width of thekey extends along the length of opening 26 partially between thesuperior 22 and inferior 24 surfaces. The width of the inserter key issized such that it is greater than a height “H.sub.2” of opening 28,which releasably secures the inserter to implant 10. The inserter may beremoved by rotating it 90 degrees which generally aligns the width ofthe key with the longitudinal axis 30 of opening 28, and then retractingthe inserter from implant 10.

In an exemplary embodiment, when implant 10 is used to fuse adjacentcervical vertebrae, the generally trapezoidal shape of inferior surface24, including the rounded portions 21 of leading end 14, may match thegeneral shape of cervical vertebral bodies. Also, in this exemplaryembodiment, the dome-shaped superior surface 22 may generally matchcervical endplate anatomy and the generally flat inferior surface 24 maymate with a flat inferior endplate in the cervical disc space or asurgically-created flat surface of a vertebral body during ahemi-vertebrectomy. Body 10 may be made from a metal, which may be aporous metal. The use of a porous metal enhances bony ingrowth. Oneexample of such a material is Trabecular Metal™, which is marketed byZimmer Spine, Inc., of Edina, Minn. Embodiments of this material arealso described in several U.S. patents, including, for example, U.S.Pat. Nos. 5,443,515 and 6,063,042, each disclosure of which is expresslyincorporated by reference herein in its entirety.

Implants 10 may be inserted by a variety of surgical approaches,including, but not limited to an anterior approach, a lateral(transverse) approach, a posterior approach, or postero-lateral approachby engaging the implant 10 with an instrument, such as an inserter. Inthe exemplary embodiment of implant 10 illustrated in FIGS. 1-7 anddiscussed above, openings 26 and 28 may be used to receive an inserter.However, in other embodiments, implant 10 may include grooves,indentations, slots or other surface deficits that allow the inserter toengage implant 10. For example, the trailing end 16 of body 12 ofimplant 10 may include holes, such as a circular hole or holes that matewith prongs on the inserter. Alternatively, body 12 may include two ormore square or rectangular surface deficits cut into the superior 22 andinferior 24 surfaces proximate trailing end 16 that may be engaged bythe inserter. In other embodiments, slots or grooves may be formed ineach of the sides 18, 20. The slots or grooves may be partially formedinto and engaged at the trailing end 16 by the inserter. The slots orgrooves may be formed such that a portion of the implant 10 forms apositive stop for the inserter instrument. Alternatively, the slots orgrooves may extend the length of the sides 18, 20 of body 12.

While the present invention has been illustrated by the description ofand exemplary embodiments thereof, and while the embodiments have beendescribed in considerable detail, it is not intended to restrict or inany way limit the scope of the appended claims to such detail.Additional advantages and modifications will readily appear to thoseskilled in the art. The invention in its broader aspects is thereforenot limited to the specific details, representative apparatus andmethods and illustrative examples shown and described. Accordingly,departures may be made from such details without departing from thescope or spirit of Applicants' general inventive concept.

What is claimed:
 1. A spinal implant comprising: a porous bodycomprising a leading end, a trailing end, a superior surface and aninferior surface, the porous body having a leading portion and atrailing portion defined by a midline dividing a length of the body inhalf; and the body defining only a single internal void, the void beinga T-shaped void in the porous body, the T-shaped void defined by a firstportion extending from a single opening in the trailing end to alocation within the trailing portion, and a second portion extendingfrom the first portion toward a single opening in the superior surfaceand toward a single opening in the inferior surface, the entire T-shapedvoid located only within the trailing portion.
 2. The implant of claim1, wherein the first portion of the void has a height and a width,wherein the height is smaller than the width, wherein the first andsecond portions of the void are configured for receipt of an inserterinstrument to insert the implant between vertebral bodies.
 3. Theimplant of claim 1, wherein the trailing end is convex.
 4. The implantof claim 1, wherein the inferior surface has a generally trapezoidalshape.
 5. The implant of claim 1, wherein the superior surface isgenerally dome-shaped, being convex between the leading and trailingends and convex between first and second sides.
 6. The implant of claim1, wherein first and second sides of the porous body are generallystraight and diverge away from one another from the leading end to thetrailing end.
 7. The implant of claim 1, wherein at least a portion ofthe leading end is generally straight.
 8. The implant of claim 1,wherein the body is made of metal.
 9. The implant of claim 1, whereinthe leading end is a posterior end and the trailing end is an anteriorend.
 10. A spinal implant comprising: a porous body comprising a leadingend, a trailing end, a superior surface and an inferior surface, theporous body having a length extending between the leading end and afurthest point on the trailing end, the body having a leading portionand a trailing portion defined by a midline dividing the length in half,the body defining only two internal voids; a first internal void locatedentirely within the trailing portion, the first void defined by only asingle opening in the superior surface and only a single opening in theinferior surface; and a second internal void located entirely within thetrailing portion, the second void defined by only a single openingcommunicating with the first void and only a single opening through thetrailing end, the entire second void located only within the trailingportion, the first and second voids configured for receipt of aninserter instrument to insert the implant between vertebral bodies. 11.The implant of claim 10, wherein the trailing end is convex.
 12. Theimplant of claim 10, wherein the superior surface is generallydome-shaped, being convex between the leading and trailing ends andconvex between first and second sides.
 13. The implant of claim 10,wherein the inferior surface has a generally trapezoidal shape.
 14. Theimplant of claim 10, wherein first and second sides of the porous bodyare generally straight and diverge away from one another from theleading end to the trailing end.
 15. The implant of claim 10, whereinthe body is made of metal.
 16. A spinal implant comprising: a porousbody comprising a leading end, a trailing end, a superior surface, andan inferior surface, the body having only a single internal void, thevoid being a T-shaped void, the T-shaped void having only threeopenings: a first opening through the superior surface; a second openingthrough the inferior surface, wherein the superior and inferior surfaceseach define a surface area of the body, the first and second openingsoccupying substantially less than half the surface area of each of thesuperior and inferior surfaces of the body; and a third opening throughthe trailing end; wherein the void is configured for receipt of aninserter instrument to insert the implant between vertebral bodies,wherein the body has a length extending between the leading end and afurthest point on the trailing end, the body having a leading portionand a trailing portion defined by a midline dividing the length in half,the entire void located only within the trailing portion.
 17. Theimplant of claim 16, wherein the superior surface is generallydome-shaped, being convex between the leading and trailing ends andconvex between first and second sides of the porous body.
 18. Theimplant of claim 16, wherein the inferior surface has a generallytrapezoidal shape.
 19. The implant of claim 16, wherein the trailing endis convex and first and second sides of the porous body are generallystraight and diverge away from one another from the leading end to thetrailing end.
 20. The implant of claim 16, wherein the body is made ofmetal.